Thermochemomechanical Assessment of Ground Improvement by Jet Grouting in Tunneling

Horizontal jet grouting (HJG) is employed in urban tunneling in order to reduce surface settlements and, hence, to avoid damage of infrastructure and surface buildings. The widespread use of HJG raises the question of its efficiency. In order to answer this question, sophisticated thermochemomechanical material models for jet-grouted soil mass and shotcrete are employed in the context of plane-strain finite element analyses. For these analyses, the process of ground improvement, the excavation of the tunnel, and the installation of the shotcrete lining are considered. The obtained results provide first insight into the load-carrying behavior of the compound structure consisting of the jet-grouted soil mass, the shotcrete lining, and the surrounding soil. The influence of the different creep characteristics in jet-grouted soil mass and shotcrete, resulting in a redistribution of loading, is highlighted. Moreover, the reduction of plastic loading of the soil in consequence of HJG, which is described by means of a multisurface viscoplasticity model, is illustrated. Based on the obtained numerical results, application of HJG results in a reduction of the surface settlement by more than 50% in comparison to a tunnel which is only supported by a shotcrete lining.